In doppler mode operation of an ultrasound imaging apparatus, the operator is able to place the target gate for the doppler vector at any point in the image. Additionally the operator is able to select any of the available velocity scales for the doppler firing and change the range gate size to any one of the selectable gate sizes. All these issues affect the timing of the transmit and receive for the doppler vector firings. This flexibility provides the operator with the ability to place the target gate in a location that would require the machine to transmit a doppler vector set at the same time it should be receiving a previous firing. This is referred to as a dead zone. Since the receive elements are the same as the transmit elements, this is not possible. This situation must be prevented, otherwise, no image is displayed when the operator is attempting to fire and receive at the same time.
In an effort to overcome this problem, ultrasound imaging systems have been developed which reduce the PRF. Other systems have been developed in which the range gate is decreased and the PRF is made large. Unfortunately, changing the PRF changes what the operator intentionally selected, affecting what the operator is trying to achieve. That is, changing the PRF means that the velocity the operator is looking for is now different from the actual velocity, which is problematic such as when the operator needs to display blood flow at a particular velocity setting.
It would be desirable then to have a means for adjusting the timing or firing parameters to prevent overlap which overcomes the problems associated with the prior art.